Aerobic interval training vs. continuous moderate exercise in the metabolic syndrome of rats artificially selected for low aerobic capacity

Abstract

Aims: The recent development of a rat model that closely resembles the metabolic syndrome allows to study the mechanisms of amelioration of the syndrome by exercise training. Here, we compared the effectiveness for reducing cardiovascular risk factors by exercise training programmes of different exercise intensities.

Methods and results: Metabolic syndrome rats were subjected to either continuous moderate-intensity exercise (CME) or high-intensity aerobic interval training (AIT). AIT was more effective than CME at reducing cardiovascular disease risk factors linked to the metabolic syndrome. Thus, AIT produced a larger stimulus than CME for increasing maximal oxygen uptake (VO(2max); 45 vs. 10%, P < 0.01), reducing hypertension (20 vs. 6 mmHg, P < 0.01), HDL cholesterol (25 vs. 0%, P < 0.05), and beneficially altering metabolism in fat, liver, and skeletal muscle tissues. Moreover, AIT had a greater beneficial effect than CME on sensitivity of aorta ring segments to acetylcholine (2.7- vs. 2.0-fold, P < 0.01), partly because of intensity-dependent effects on expression levels of nitric oxide synthase and the density of caveolae, and a greater effect than CME on the skeletal muscle Ca2+ handling (50 vs. 0%, P < 0.05). The two exercise training programmes, however, were equally effective at reducing body weight and fat content.

Conclusion: High-intensity exercise training was more beneficial than moderate-intensity exercise training for reducing cardiovascular risk in rats with the metabolic syndrome. This was linked to more superior effects on VO(2max), endothelial function, blood pressure, and metabolic parameters in several tissues. These results demonstrate that exercise training reduces the impact of the metabolic syndrome and that the magnitude of the effect depends on exercise intensity.

Figures

Figure 1

Maximal oxygen uptake (VO2max) (A). Expression of peroxisome proliferator-activated receptor-γ co-activator-1α (PGC-1α) in samples from m. soleus (B). Maximal rate of re-uptake of calcium into sarcoplasmic reticulum in m. soleus (C). *Significantly different between high-intensity aerobic interval training (AIT) and continuous moderate-intensity exercise (CME) programmes (P < 0.05). §Significantly different from sedentary (SED) (P < 0.01). #Significantly different from SED (P < 0.05). Each group consisted of eight rats.

Figure 2

Endothelial function measured as a relaxation response to accumulating concentrations of acetylcholine (ach) in isolated ring segments of aorta (A) and as the concentration of acetylcholine that provoked a half-maximal response (EC50) (B). Endothelial function was also measured after incubation of 10−4 M L-NAME (C) and with accumulating concentrations of Na+ nitroprusside (D). *Significantly different between high-intensity aerobic interval training (AIT) and continuous moderate-intensity exercise (CME) programmes (P < 0.05). §Significantly different from sedentary (SED) (P < 0.01). Each group consisted of eight rats.

Figure 3

Relative expressions of the endothelial nitric oxide synthase (eNOS) (A) and heat shock protein 90 (HSP90) (B) in aorta. Caveolae density measured with an electron microscope in endothelial cells from aorta (C) and the relative expression of caveolin-1 in aorta (D). *Significantly different between high-intensity aerobic interval training (AIT) and continuous moderate-intensity exercise (CME) programmes (P < 0.05). §Significantly different from sedentary (SED) (P < 0.01). Each group consisted of eight rats.

Figure 4

Insulin action in m. soleus (A), fat (B), and liver tissue (C). pIR, phosphorylated insulin receptor. *Significantly different between high-intensity aerobic interval training (AIT) and continuous moderate-intensity exercise (CME) programmes (P < 0.05). §Significantly different from sedentary (SED) (P < 0.01). Each group consisted of eight rats.

Figure 5

Relative expression of fatty acid transporter protein 1 (FATP-1) (A) and fatty acid synthase (FAS) (B) in fat tissue. *Significantly different between high-intensity aerobic interval training (AIT) and continuous moderate-intensity exercise (CME) programmes (P < 0.05). §Significantly different from sedentary (SED) (P < 0.01). Each group consisted of eight rats.